Hydraulic brake mechanism for an air cylinder

ABSTRACT

For retarding the motion of a piston traveling on its forward stroke in an air cylinder, a hydraulic cylinder having shorter piston stroke than that of the air cylinder is mounted on its rear side in axial alignment therewith. The piston rod of the hydraulic cylinder projects into the air cylinder to be telescopically received in an axial bore formed through the rear end portion of the air cylinder piston rod. Hence, as the air cylinder piston travels forwardly in the usual manner to a predetermined point intermediate both extremities of its stroke, a larger diameter portion on the front end of the hydraulic cylinder piston rod engages the air cylinder piston at the rear end of the aforesaid axial bore. The forward motion of the air cylinder piston is thereafter retarded by the hydraulic cylinder piston also traveling forwardly against the resistance offered by hydraulic fluid in the intercommunicated chambers of the hydraulic cylinder. The passageway intercommunicating the hydraulic fluid chambers can be closed by a solenoid-operated shut-off valve whereby the air cylinder piston traveling forwardly at reduced speed as above can be stopped whenever required.

United States Patent Kondo Dec. 30, 1975 [54] HYDRAULIC BRAKE MECHANISMFOR AN AIR CYLINDER [21] Appl. No.: 427,847

Sept. 18,1973 Japan.................... 43405140 Apr. 14', 1973 Japan48-42427 [52] US. Cl. 92/9; 92/10; 92/12; 92/143; 188/300; 188/318 [51]Int. Cl. FlSB 15/2 [58] Field of Search 92/8, 9, 10,11, 12, 143',188/300 X, 318 X [56] References Cited UNITED STATES PATENTS 2,605,7518/1952 Perry et al. 92/9 X 2,857,789 10/1958 Robinson 92/8 X 2,991,7607/1961 Rhine 92/11 X 3,043,278 7/1962 Ackerman 92/11 X 3,313,214 4/1967Ackerman 92/8 3,463,036 8/1969 O'Connor 92/11 X 3,584,712 6/1971Dickinson..... 188/318 X 3,659,684 5/1972 Porter 188/300 X 3,678,8057/1972 Weyman 4 92/1 1 3,824,900 7/1974 McLelland 92/8 3,830,139 8/1974Wachsman et a1, 92/9 JIIIIII'II'IIIIIIIIII Primary Examiner-Martin P.Schwadron Assistant Examiner-Abraham Hershkovitz Attorney, Agent, orFirm-l-lill, Gross, Simpson, Van Santen, Steadman, Chiara & Simpson [57]ABSTRACT For retarding the motion of a piston traveling on its forwardstroke in an air cylinder, a hydraulic cylinder having shorter pistonstroke than that of the air cylinder is mounted on its rear side inaxial alignment therewith. The piston rod of the hydraulic cylinderprojects into the air cylinder to be telescopically received in an axialbore formed through the rear end portion of the air cylinder piston rod.Hence, as the air cylinder piston travels forwardly in the usual mannerto a predetermined point intermediate both extremities of its stroke, alarger diameter portion on the front end of the hydraulic cylinderpiston rod engages the air cylinder piston at the rear end of theaforesaid axial bore. The forward motion of the air cylinder piston isthereafter retarded by the hydraulic cylinder piston also travelingforwardly against the resistance offered by hydraulic fluid in theintercommunicated chambers of the hydraulic cylinder. The passagewayintercommunicating the hydraulic fluid chambers can be closed by asolenoid-operated shut-off valve whereby the air cylinder pistontraveling forwardly at reduced speed as above can be stopped wheneverrequired.

4 Claims, 2 Drawing Figures US. Patent Dec. 30, 1975 Sheet 1 on3,929,057

U.S. Patent Dec. 30, 1975 Sheet 2 of2 3,929,057

HYDRAULIC BRAKE MECHANISM FOR AN AIR CYLINDER BACKGROUND OF THEINVENTION This invention relates to an apparatus for hydraulicallycontrolling the speed of a piston in an air cylinder.

PRIOR ART As is well known, the air cylinder of prior art constructionis used extensively as a feed mechanism in some machine tools or otherclasses of manufacturing equipment. It is often desired, however, that acutting tool or the like be fed toward the work, or vice versa, atrelatively high speed and then at appropriately reduced speed as thetool starts actually machining the work. To this end the air cylinderhas been used in combination with a hydraulic cylinder of equal pistonstroke either in serial or tandem arrangement.

It will be apparent that such prior art arrangement results in largespace requirement and high manufacturing costs as the hydraulic cylinderis required to have as long piston stroke as the air cylinder. As afurther disadvantage, the hydraulic circuit of the prior art arrangementmust be equipped with highly involved valving to effect the desiredchange in the feed speed of the cutting tool or the like.

SUMMARY OF THE INVENTION In view of the noted deficiencies of the priorart, it is an object of this invention to provide a novel and advancedapparatus for controlling the speed of a piston in an air cylinder, insuch a manner that the forward motion of the piston becomes retarded ata predetermined point intermediate both extremities of its stroke.

Another object of the invention is to provide an ap paratus of the abovedescribed character, wherein a hydraulic cylinder of considerablyshorter piston stroke than that of the air cylinder is coupled directlythereto in serial arrangement, with the front end portion of thehydraulic cylinder piston rod telescopically received in an axial boreformed through the rear end portion of the air cylinder piston rod, sothat the overall system is rendered highly compact in size andinexpensive in construction.

A further object of the invention is to provide an apparatus of thecharacter described, including a regu lating valve whereby the degree ofreduction in the speed of the air cylinder piston is regulatable asdesired.

A further object of the invention is to provide an apparatus of thecharacter described, including a shutoff valve typically operated by asolenoid to arrest the motion of the air cylinder piston as it travelsforwardly at reduced speed.

A still further object of the invention is to provide an apparatus ofthe character described, wherein the depth or axial length of the axialbore formed through the rear end portion of the air cylinder piston rodis variable to adjustably change the distances the air cylinder pistonis driven at high and reduced speeds, respectively, on its forwardstroke.

In order to control the speed of a piston in an air cylinder assembly ofwell known construction in accordance with the concepts of thisinvention, there is employed a hydraulic cylinder assembly of shorterpiston stroke than that of the air cylinder assembly. The hydrauliccylinder assembly comprises a sleeve or cylinder fixedly supported onthe rear side of that of the air cylinder assembly in coaxialrelationship thereto, a piston slidably mounted within the cylinder topressure tightly divide its interior into front and rear hydraulic fluidchambers which are intercommunicated through a passageway, and a pistonrod securely coupled at its rear end to the piston and slidablyextending into the air cylinder assembly to have its front end portiontelescopically received in an axial bore formed through the rear endportion of the air cylinder pistion rod. The hydraulic cylinder pistonrod carries a flange or larger diameter portion on its front end whichis adapted to engage the air cylinder piston at the rear end ofthc saidaxial bore.

Hence, as the air cylinder piston travels forwardly in the usual mannerto a predetermined point intermedi ate both extremities of its stroke,its motion becomes retarded by the hydraulic cylinder piston as thelatter is then caused to start traveling forwardly in step with the aircylinder piston against the resistance offered by hydraulic fluidflowing from the front to the rear hydraulic fluid chamber through thepassageway. Typically, this passageway is equipped with a regulatingvalve adapted to regulate the rate of flow of the hydraulic fluidtherethrough and hence to adjust the degree of reduction in the speed ofthe air cylinder piston. The passageway can be further equipped with ashut-off valve capable of completely closing the same to arrest theforward motion of the air cylinder piston. Thus, if the passageway isalternately opened and closed by the shutoff valve during the forwardstroke of the hydraulic cylinder piston, the air cylinder piston can becaused to travel forwardly at reduced speed in an intermittent manner.Such intermittent piston motion is highly useful in some machiningoperations.

The features which are believed to be novel and characteristic of thisinvention are set forth with particularity in the appended claims. Theinvention itself, however, both as to its configuration and mode ofoperation, together with the further objects and advantages thereof,will be best understood from the following description taken inconjunction with the accompanying drawings which illustrate, by way ofexample only, some preferred embodiments of the invention and in both ofwhich like reference characters denote like parts.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. I is a longitudinal or axialsectional view of an arrangement formed in accordance with theprinciples of this invention; and

FIG. 2 is a similar view showing another preferred embodiment of theinvention.

DESCRIPTION OF THE PREFERRED EMBODIMENTS With reference to FIG. I, thereference numeral 10 generally designates an air cylinder assembly thepiston speed of which is to be controlled in accordance with theinventive concepts. The air cylinder assembly 10 includes a sleeve orcylinder ll pressure-tightly closed at its left hand end, as seen in thedrawing, by a front end cap 12 and at its right hand end by a rear endcap I3. A piston 14 is slidably but pressure-tightly mounted within thecylinder 11 thereby dividing its interior into a pair of opposed airchambers 15 and I6, and a piston rod 17 securely coupled at its righthand end to the piston 14 slidably but pressure-tightly extends through3 the front end cap 12 in axial alignment with the cylinder 1].

A pair of U-type sealing rings 18 are fitted in an opposed manner inannular recesses formed in spaced parallel relationship on thecircumference of the piston 14. Air inlet/outlet ports 19 and 20 areformed through the front and rear end caps 12 and 13, respectively, tocommunicate the respective air chambers 15 and 16 with a source ofcompressed air, not shown, through pressure conduits having suitablevalving such that air under pressure will be introduced alternately intothe two opposed air chambers in the operation of this air cylinder. Itis to be noted, however, that the construction of the air cylinderassembly 10 as so far described is well known and, by itself, does notconstitute a part of this invention.

In order to control the speed of the piston 14 of this air cylinderassembly 10 in the manner previously set forth, a hydraulic cylinderassembly generally designated by the numeral 21 is mounted in serialrealtionship to the air cylinder assembly. The hydraulic cylinderassembly 21 also includes a sleeve or cylinder 22 pressure-tightlyclosed at its front or left hand end by the rear end cap 13 of the firstmentioned cylinder 11 and at its rear or right hand end by its own rearend cap 23. A piston 24 is slidably but pressure-tightly mounted withinthe cylinder 22 to divide its interior into a pair of opposed hydraulicfluid chambers 25 and 26. It will be noted from the drawing that thestroke of this piston 24 within the cylinder 22 is considerably shorterthan the piston stroke within the cylinder 11.

A piston rod 27 securely coupled at its rear or right hand end to thehydraulic cylinder piston 24 slidably but pressure-tightly extendsthrough the end cap 13 and further through the air cylinder piston 14 tohave its front or left hand end portion telescopically received in anaxial bore 28 of the air cylinder piston rod 17. This axial bore 28 hasa diameter sufficient to slidably accommodate a flange or largerdiameter portion 29 formed on the left hand end of the hydrauliccylinder piston rod 27 and extends from the right hand end of the aircylinder piston rod 17 to a prescribed point intermediate both endsthereof. The right hand extremity of the axial bore 28 is closed by theair cylinder piston 14, and a shock absorber such for example as a sheetof suitably elastic material is provided at 30 to minimize the impactenergy that may be produced as the larger diameter portion 29 on thehydraulic cylinder piston rod 27 engages the air cylinder piston 14 byits shoulder 31. Preferably, an air vent should be formed as at 32, anda groove or aperture should be formed longitudinally on or through thelarger diameter portion 29 of the hydraulic cylinder piston rod 27, inorder to assure its smooth sliding motion within the axial bore 28 ofthe air cylinder piston rod 17.

A plurality of bores 33 are formed eccentrically through the hydrauliccylinder piston 24 substantially in annular arrangement, and these bores33 are normally closed by a flap 34 of annular shape on the side of theleft hand hydraulic fluid chamber 25. The flap 34 is somewhat looselyfitted over a flanged sleeve 35 fixedly supported on the hydrauliccylinder piston rod 27 between its shoulder 36 and the hydrauliccylinder piston 24 and is yieldably urged toward the bores 33 by springmeans 37 supported by the flanged sleeve 35. The flap 34 in combinationwith the spring means 37 is adapted to perform the function of a checkvalve, permitting the flow of hydraulic fluid such as oil through 4 thebores 33 only from the right to the left hand hydraulic fluid chamberduring the rightward or return stroke of the hydraulic cylinder piston24.

The left and right hand hydraulic fluid chambers 25 and 26 havehydraulic fluid inlet/outlet ports 38 and 39 formed in the end caps 13and 23, respectively, and these ports 38 and 39 are intercommunicatedthrough a passageway 40 which is equipped with a regulating valve 41 ofthe type operated manually to regulate the flow rate of the hydraulicfluid therethrough and with a shut-off valve 42 of the type operated bya solenoid mechanism 43 of well known construction to completely closethe passageway 40 as required, as hereinafter set forth in more detail.

The reference numeral 44 generally indicates a compensating mechanismadapted to compensate for the undersupply of hydraulic fluid which willtake place in the right hand hydraulic fluid chamber 26 as the hydrauliccylinder piston 24 moves on its leftward or forward stroke, due largelyto the presence of the hydraulic cylinder piston rod 27 in the left handhydraulic fluid chamber 25. The compensating mechanism 44 includes acylinder 45 closed at both ends thereof, and a piston 46 slidablymounted therein. The right hand one of the two opposed chambers definedwithin the cylinder 45 by the piston 46 is pressure tight. The piston 46is yieldably urged, as by a helical compression spring 47, toward thatone pressure-tight chamber of the cylinder 45 to constantly forcehydraulic fluid into the right hand hydraulic fluid chamber 26 of thehydraulic cylinder assembly 21 through a passageway 48 at a prescribedpressure. The right hand hydraulic fluid chamber 26 can thus be heldfilled with hydraulic fluid regardless of the position of the hydrauliccylinder piston 24 within the cylinder 22.

In the operation of this first preferred embodiment of the invention, itis assumed that air under pressure is first delivered into the righthand air chamber 16 of the air cylinder assembly 10 through the airinlet/outlet port 20, thereby causing the air cylinder piston 14 totravel toward the front end cap 12 at relatively high speed while theair which has been trapped within the left hand air chamber 15 is causedto escape through the other air inlet/outlet port 19. Forward thrust isthus imparted to the air cylinder piston rod 17. However, as the aircylinder piston 14 reaches the prescribed point within the cylinder 11at which the air cylinder piston 14 closing the right hand extremity ofthe axial bore 28 becomes engaged by the shoulder 31 on the hydrauliccylinder piston rod 27 through the shock absorber 30, the hydrauliccylinder piston 24 becomes operative to retard the forward motion of theair cylinder piston 14 and hence of the air cylinder piston rod 17.

Thereafter, as the air under pressure is further introduced into theright hand air chamber 16, the air cylinder piston 14 continuestraveling to the left on its forward stroke at reduced speed since nowits motion is retarded by the hydraulic cylinder piston 24 traveling inthe same direction against the resistance offered by the hydraulic fluidwithin the left hand hydraulic fluid chamber 25. During this forwardstroke of the hydraulic cylinder piston 24, its bores 33 are held closedby the aforesaid check valve means comprising the flap 34 and the springmeans 37, so that the hydraulic fluid within the left hand hydraulicfluid chamber 25 is forced out into the hydraulic fluid inlet/outletport 38 and flows into the right hand hydraulic fluid chamber 26 throughthe passageway 40 at a rate determined by the regulating valve 41.

If the solenoid mechanism 43 is energized while the air cylinder piston14 is thus traveling on its forward stroke at reduced speed, its plungerretracts to cause the shut-off valve 42 to completely close the passageway 40 intercommunicating the hydraulic fluid chambers 25 and 26. Theforward motion of the hydraulic cylinder piston 24 is then arrested, andthe air cylinder piston 14 is also caused to stop rapidly through thehydraulic cylinder piston rod 27. As the solenoid mechanism 43 issucceedingly de-energized, the shut-off valve 42 reopens the passageway40 thereby permitting the flow of the hydraulic fluid from the left handchamber 25 to the right hand chamber 26, so that the air cylinder piston14 resumes traveling on its forward stroke at reduced speed. Thus, byalternately energizing and de-energizing the solenoid mechanism 43 whilethe hydraulic cylinder piston 24 is traveling on its for ward stroke,the air cylinder piston 14 can be caused to travel forwardly at reducedspeed in an intermittent manner.

Upon completion of the forward stroke of the air cylinder piston 14, airunder pressure is to be introduced into the left hand air chamberthrough the air inlet/outlet port 19. The air cylinder piston 14 startstraveling to the right on its return stroke at relatively high speedcausing the air within the right hand air chamber 16 to escape throughthe air inlet/outlet port 20. As the left hand extremity of the axialbore 28 in the air cylinder piston rod I7 comes into contact with thelarger diameter portion 29 on the left hand end of the hydrauliccylinder piston rod 27, the hydraulic cylinder piston 24 also is causedto start traveling to the right on its return stroke through thehydraulic cylinder piston rod 27. Since then the hydraulic fluid withinthe right hand hydraulic fluid chamber 26 is permitted to flow into theleft hand hydraulic fluid chamber 25 through the bores 33 as aforesaid,the hydraulic cylinder piston 24 is capable of traveling back to theposition of FIG. 1 without any substantial resistance. Thus the aircylinder piston I4 is allowed to complete its return stroke with hardlyany appreciable reduction in speed.

Illustrated in FIG. 2 is another preferred embodiment of the invention,in which the working length of the axial bore 28 formed in the aircylinder piston rod 17 is made adjustable to change the position inwhich the speed of the air cylinder piston 14 traveling on its forwardstroke is reduced from high to low level. In the succeeding descriptionof this second embodiment of the invention, parts corresponding to thoseof the preceding embodiment are indicated by like reference charactersand are not explained in any detail.

As seen in FIG. 2, an axial bore 28a extending from the right hand endof a piston rod [70 of an air cylinder assembly 10a toward the left mayhave a length appro priately greater than that of the axial bore 28 inthe FIG. 1 embodiment. The left hand extremity of the axial bore 28a isdefined by a step 50 and is open to a second axial bore 51 of reduceddiameter extending to the left hand end of the air cylinder piston rod170. The second axial bore 51 is adapted to screw-thrcadedly receive anadjusting rod 52 having a flange or larger diameter portion 53 on itsright hand end which is slidably received in the first mentioned axialbore 280. A nut 54 is fitted over the externally screw-threaded lefthand end portion of the adjusting rod 52 projecting out of the secondaxial bore 51. Other details of con- 6 struction are as set forthpreviously with reference to FIG. 1.

The operation of this second embodiment also sub stantially follows suitafter that of the FIG. 1 embodiment. However, by turning the adjustingrod 52 relative to the air cylinder piston rod 17a after loosening thenut 54, the working length of the first axial bore 280 can be varied asdesired. Generally, the farther the larger diameter portion 53 of theadjusting rod 52 is located away from the right hand extremity of thefirst axial bore 28a, the greater is the distance the air cylinderpiston 14 is fed at relatively high speed on its forward stroke, and thesmaller is the distance the air cylinder piston is fed at reduced speed.Conversely, the closer the larger diameter portion 53 of the adjustingrod 52 is located to the right hand extremity of the first axial bore28a, the smaller is the distance the air cylinder piston 14 is fed atrelatively high speed on its forward stroke, and the greater is thedistance the air cylinder piston is fed at reduced speed.

It is believed that the preferred embodiments shown and described hereinare well calculated to accomplish the objects previously set forth.However, the general design or individual parts of the invention asexplained above may be varied according to requirements in regards tomanufacture and production therof, while still remaining within thespirit and scope of the invention as sought to be defined by theappended claims.

What is claimed is:

I. A feed mechanism for a machine tool comprising in combination:

a. a double-acting pneumatic cylinder assembly having a first piston anda piston rod having its inner end secured to and terminating within saidpiston, said rod having an axially hollow portion and an outer end forbeing connected to a load, said rod being subjected to compressionalaxial forces as it is extended during its working stroke and to tensionduring retraction thereof, there being means communicating the interiorof said rod with that side of said first piston which is the lowpressure side during the working stroke and the high pressure sideduring retraction;

b. a double-acting hydraulic cylinder assembly connected concentricallywith said pneumatic cylinder assembly, and having a second piston, ofsmaller diameter and lesser stroke than said first piston, and a secondpiston rod having one end rigidly secured to said second piston, saidsecond piston rod having a portion at all times projecting through andslidably guided by said first piston into said hollow portion of saidpiston rod;

c. the other end of said second piston rod having a flange engaging thelow-pressure side of said first piston during the working stroke totension said second piston rod for thereby pressurizing the side of saidsecond piston which is closer to said first piston, said flange beingengaged by an abutment in said axially hollow piston rod during thereturn stroke;

d. impact absorbing means for acting between said flange of said secondpiston rod and said first piston;

e. a throttling passageway interconnecting the oppo site sides of saidsecond piston during a working stroke, there being a power-actuatedshut-off valve in said throttling passageway for hydraulically arrestingthe second portion during the working 7 stroke;

f. a separate second hydraulic cylinder assembly including a thirdpiston of the single-acting spring return type and fluidly connected tothe end of the first-named hydraulic cylinder which is more remote fromsaid first piston and disposed in radially spaced relation to said firsthydraulic cylinder assembly; and

g. a check valve directed to freely interconnect the opposite sides ofsaid second piston during a return stroke.

2. A feed mechanism according to claim 1, said check valve comprising: aplurality of bores in said second piston, an annular washer of resilientmaterial disposed against said second piston at its bores, spring meansnormally biasing said resilient washer in a direc- 8 tion away from saidpneumatic cylinder assembly toward said second piston, and a flangedsleeve secured to said second piston rod against the flange of whichsaid spring means reacts, said sleeve centering said washer and saidspring means.

3. A feed mechanism according to claim 1 in which the inner end of saidhollow piston rod is closed by an annular portion of said first pistonthrough which said second rod projects.

4. A feed mechanism according to claim 1 including adjustable means insaid axially hollow portion of said piston rod for positioning saidabutment which initiates the return stroke of said second piston andopening of said check valve.

1. A feed mechanism for a machine tool comprising in combination: a. adouble-acting pneumatic cylinder assembly having a first piston and apiston rod having its inner end secured to and terminating within saidpiston, said rod having an axially hollow portion and an outer end forbeing connected to a load, said rod being subjected to compressionalaxial forces as it is extended during its working stroke and to tensionduring retraction thereof, there being means communicating the interiorof said rod with that side of said first piston which is the lowpressure side during the working stroke and the high pressure sideduring retraction; b. a double-acting hydraulic cylinder assemblyconnected concentrically with said pneumatic cylinder assembly, andhaving a second piston, of smaller diameter and lesser stroke than saidfirst piston, and a second piston rod having one end rigidly secured tosaid second piston, said second piston rod having a portion at all timesprojecting through and slidably guided by said first piston into saidhollow portion of said piston rod; c. the other end of said secondpiston rod having a flange engaging the low-pressure side of said firstpiston during the working stroke to tension said second piston rod forthereby pressurizing the side of said second piston which is closer tosaid first piston, said flange being engaged by an abutment in saidaxially hollow piston rod during the return stroke; d. impact absorbingmeans for acting between said flange of said second piston rod and saidfirst piston; e. a throttling passageway interconnecting the oppositesides of said second piston during a working stroke, there being apower-actuated shut-off valve in said throttling passageway forhydraulically arresting the second portion during the working stroke; f.a separate second hydraulic cylinder assembly including a third pistonof the single-acting spring-return type and fluidly connected to the endof the first-named hydraulic cylinder which is more remote from saidfirst piston and disposed in radially spaced relation to said firsthydraulic cylinder assembly; and g. a check valve directed to freelyinterconnect the opposite sides of said second piston during a returnstroke.
 2. A feed mechanism according to claim 1, said check valvecomprising: a plurality of bores in said second piston, an annularwasher of resilient material disposed against said second piston at itsbores, spring means normally biasing said resilient washer in adirection away from said pneumatic cylinder assembly toward said secondpiston, and a flanged sleeve secured to said second piston rod againstthe flange of which said spring means reacts, said sleeve centering saidwasher and said spring means.
 3. A feed mechanism according to claim 1in which the inner end of said hollow piston rod is closed by an annularportion of said first piston through which said second rod projects. 4.A feed mechanism according to claim 1 including adjustable means in saidaxially hollow portion of said pistoN rod for positioning said abutmentwhich initiates the return stroke of said second piston and opening ofsaid check valve.